[Discuss-gnuradio] Re: Measure BER

[Patrick Strasser]

irene159 schrieb am 2008-01-21 16:01:
> Hi! 
>
> 2) When comparing data sent and data received, how can we detect bit lost in
> order to avoid clock shifting? In other words, if I’m sending “11010110” for
> example, and that the 4th bit is lost, a simple comparison will compare tx :
> “11010110” with rx : “1100110”. Detecting a lost is easy because the number
> of bits in reception will be inferior to the number of bits sent, but how
> can continue to compare the rest correctly?

You would use a known sequence which you synchronize on. This can be a 
pseudo-noise sequence or a long pattern. It should have low 
autocorrelation except for a shift of 0. In hardware you would run the 
sequence a slightly lower or higher rate and try to lock. If the 
receiver-generated and the received sequence are approximately equal, 
you get lock and run the sequence at the right speed.

In software? Dunno, is correlating fast and robust?

Patrick
--
Engineers motto: cheap, good, fast: choose any two
Patrick Strasser <patrick dot strasser at tugraz dot at>
Student of Telematik, Techn. University Graz, Austria